Typha is an iconic wetland plant found worldwide. Hybridization and anthropogenic disturbances have resulted in large increases in Typha abundance in wetland ecosystems throughout North America at a cost to native floral and faunal biodiversity. As demonstrated by three regional case studies, Typha is capable of rapidly colonizing habitats and forming monodominant vegetation stands due to traits such as robust size, rapid growth rate, and rhizomatic expansion. Increased nutrient inputs into wetlands and altered hydrologic regimes are among the principal anthropogenic drivers of Typha invasion. Typha is associated with a wide range of negative ecological impacts to wetland and agricultural systems, but also is linked with a variety of ecosystem services such as bioremediation and provisioning of biomass, as well as an assortment of traditional cultural uses. Numerous physical, chemical, and hydrologic control methods are used to manage invasive Typha, but results are inconsistent and multiple methods and repeated treatments often are required. While this review focuses on invasive Typha in North America, the literature cited comes from research on Typha and other invasive species from around the world. As such, many of the underlying concepts in this review are relevant to invasive species in other wetland ecosystems worldwide.

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Since European settlement, over 50 % of coastal wetlands have been lost in the Laurentian Great Lakes basin, causing growing concern and increased monitoring by government agencies. For over a decade, monitoring efforts have focused on the development of regional and organism-specific measures. To facilitate collaboration and information sharing between public, private, and government agencies throughout the Great Lakes basin, we developed standardized methods and indicators used for assessing wetland condition. Using an ecosystem approach and a stratified random site selection process, birds, anurans, fish, macroinvertebrates, vegetation, and physico-chemical conditions were sampled in coastal wetlands of all five Great Lakes including sites from the United States and Canada. Our primary objective was to implement a standardized basin-wide coastal wetland monitoring program that would be a powerful tool to inform decision-makers on coastal wetland conservation and restoration priorities throughout the Great Lakes basin.

Climate change is predicted to reduce Laurentian Great Lakes water levels, altering coastal wetland ecosystems and potentially stimulating invasive macrophytes, like Typha X glauca. Recent prolonged low water levels, which climaxed in 2007, created conditions comparable to those predicted by climate change science. In 2008, we examined ecosystem and plant community properties in 14 intact northern Great Lakes coastal wetlands and compared community data with data from a 1987-1989 high-water period, before T. X glauca invasion. In 2008, T. X glauca occurred in 50% of wetlands and 16% of plots; was associated with reduced Floristic Quality and increased soil organic matter, soil nutrients, and leaf litter (all p<0.05); and plant community composition had shifted and was more homogeneous than in 1988 (both p<0.05). Additionally, T. X glauca was more dominant when growing behind barrier beach ridges, which form in high-water conditions and persist in low-water, than in lake-exposed marshes (p<0.05), revealing a physiographic mechanism for increased dominance. Beach ridges protect T. X glauca from wave and seiche energy, and as water levels decline, these energyinsulating microtopographic features will likely stimulate further invasion and dominance by T. X glauca, even in high quality wetlands.